One day, you walk down a street in your neighborhood and everyone has a Yankees cap on their head, a Yankees windbreaker on their backs. You walk into a saloon, there’s Yankees talk filling every stool.

And you practically need a court order to get a Mets game on the TV.

The next day, you see them: Mets fans rising out of a long winter’s hibernation. Mets bumper stickers. Mets T-shirts. Kids wearing Beltran jerseys. It’s a slow process, but it does happen.

It has happened. Eventually, it will happen again.

Is it happening now?

Is this becoming a Mets town again?

This week we may start to get a sense if it is. The Mets are flying, they have the best record in the National League, they’re playing as well as they’ve played in damn near 20 years. They get three games with the Phillies starting tonight, and if they take two out of three they’ll have an eight-game loss-column lead on the rest of the NL East, and it’ll be time to start calculating a magic number (which, for the record, stands at 94 this morning).

The Yankees – battered, bruised, bleeding, yet still only a game out of first place – get the Indians, a team that sure knows how to pound the baseball. At a time when the Yankees’ pitching staff is covered with more question marks than the Riddler, it’s a less-thanideal twist in the schedule.

But really, this isn’t all about performance. It’s about buzz. It’s about keeping your ear to the sidewalk, hearing what the people are talking about. Right now, Yankees remain the dominant team in the market, they sell 50,000 tickets every night, TV ratings are high, merchandise still flies off shelves, and there’s 12 uninterrupted years of success to draw upon.

It’s just a smaller difference now. And there are weekends, like the one just past, when you take a stroll through town and it’s starting to look and sound and feel an awful lot like the middle ’80s again. Not everywhere. Not all the time. Just enough to make you stop, and think, and wonder.

Baseball has always been different around here, everyone knows that. The Giants are, and always have been, the dominant football team in town even during those years when Joe Namath was the dominant personality in town. The Nets could rack up playoff berths from now until forever, from Jersey to Uniondale back to Jersey and over to Brooklyn, and they’ll never swim across the moat and topple the Knicks’ flag, no matter how much James Dolan desecrates it. And the Rangers will own the city’s hockey soul no matter how many Cups the Islanders and Devils collect.

These are law.

But baseball plays by different rules, even in the 44-plus seasons when it’s only been a two-team town. The Mets were born at a time when the city was bored by the Yankees, they filled a crevasse left by two fleeing teams, and for the first dozen or so years of their existence they ruled the town with an iron fist. Then the Yankees were reborn in the mid’70s, the Mets fell into disrepair and Mets fans became a more endangered species than the spotted owl.

It didn’t seem possible that things could ever switch back again, but they did, and in a big way, and by the time the Mets had assembled their mid-’80s powerhouse they were drawing almost a million fans more per season than the Yankees were. And then, around 1993 or so, things switched back one more time, stayed that way, seemed like they might stay that way forever.

Only we should know by now that in baseball New York, nothing is truly forever.

The deed still belongs to the Yankees, it’s theirs to lose, the Mets’ to steal. The Mets can take a few more steps over the wall this week, make it as fair a fight as it’s been in a long, long while. In a season so interesting on both sides of the Triboro that you barely want to blink for fear of missing something, it’s just another reason to savor the summer.